This sounds like a nano-cube... if so, and you are using the stock enclosure, you are gonna have a hard time adding lights to the built-in canopy unless you are a
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DIYer.
You do know you can't just put bigger bulbs in, right (again, assuming we're dealing with a nano and stock canopy)...
If you want to keep an anemone that badly, one thing you might look into is the K-2 Viper 150 Metal Halide. If you have a nano, you'll need to remove the top all together (it's always fun to go topless), and the fixture just clamps onto the tank. They are pricey (maybe 150-200), but they work and it will be more than enough light for an anemone. I have one on my 24g nano and it works great. If you want to check it out, here is a page on my site where I upgraded from one to the other.
http://www.davestanks.com/?targetpag...GalUpgrade.asp
Bear in mind though that anemones move and in a small tank, they may wreak havok... just a heads up.